A Digital Rights Management (DRM) refers to a system technology for safely protecting a right for digital contents and systematically managing it. The DRM provides a protecting and managing scheme for preventing an illegal copy of the content, acquiring DRM contents RO, and creating and transferring the content.
FIG. 1 illustrates a construction of a DRM system. The DRM system controls content issued to a user by a content provider to be consumed only in a right-limit of RO. Here, the content provider refers to an entity corresponding to a Content Issuer (Cl) and/or a Rights Issuer (RI).
The Cl issues a protected content using a particular encryption key so as to protect the content from users having no access right therefor, while the RI issues RO required to consume the protected content.
A DRM agent is mounted in a terminal thus to receive the protected content and the RO. The DRM agent then analyzes ‘permission’ and/or ‘constraint’ included in the RO and thus changes the protected content into a format which is usable in the corresponding terminal, thereby controlling the use of the content. Here, the RO for the DRM content may include various types of constraints which is employed when consuming the corresponding DRM content and examples of types of constraints, related to consuming the corresponding DRM content, is given as follows: ‘count’; ‘interval’; or ‘system’.
Meanwhile, there may be a case that a certain terminal to which RO for a specific DRM content has been issued employs the RO issued and simultaneously desires to temporarily share the RO together with a plurality of unspecified devices or different (other) devices all of which belong to a certain domain.